TWI690588B - Colloidal silica polishing composition and method for manufacturing synthetic quartz glass substrates using the same - Google Patents

Abstract

A polishing composition comprising a colloidal dispersion of spherical silica particles and associated silica particles as abrasive is provided. When used in the step of polishing synthetic quartz glass substrates, the polishing composition ensures a higher polishing rate than conventional colloidal silica and is effective for preventing any microscopic defects on the substrate surface, thus providing the substrate with a high smoothness. The polishing composition can be used as the ceria replacement polishing composition for polishing a lapped surface.

Description

Colloidal silicon dioxide abrasive material and method for manufacturing synthetic quartz glass substrate using the same

The present invention relates to colloidal silicon dioxide abrasives, and more specifically, to colloidal dioxide of synthetic quartz glass substrates used in cutting-edge technologies such as polishing masks, nanoimprints, and liquid crystal color filters. Manufacturing method of silicon abrasive and synthetic quartz glass substrate using the same.

When polishing synthetic quartz glass substrates used in photomasks, liquid crystal substrates, etc., abrasive materials such as cerium oxide and colloidal silica are often used as abrasive materials.

Synthetic quartz glass substrates used for polishing photomasks and liquid crystals require high flatness, high smoothness and low defects, so the surface adjustment is performed through several steps such as a lapping step and a polishing step. Manufacturing products.

The friction step is to remove the processing deformation when slicing from the ingot, and the polishing step is to mirror the substrate and improve the surface flatness and shape In the final polishing step, a colloidal silica abrasive with a small particle size is used to smooth the surface of the substrate, remove minor defects, and manufacture the substrate.

In the step of mirroring the substrate, it is known that the use of cerium oxide abrasives is more general and effective.

However, the price of rare earths has been rising recently. In order to reduce the use of cerium oxide abrasives, various researches have been conducted with the goal of replacing abrasive materials or developing recycling technologies.

For example, Japanese Patent Laid-Open No. 2009-007543 (Patent Document 1) has proposed a method of polishing a glass substrate using composite oxide particles in which zirconia is mixed with cerium oxide as an abrasive.

Furthermore, Japanese Patent Laid-Open No. 2008-270584 (Patent Document 2) shows that by using non-spherical special-shaped colloidal silica particles, the semiconductor is polished at a superior polishing rate than when the colloidal silica is generally used. Wafer method.

[Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2009-007543

[Patent Document 2] Japanese Unexamined Patent Publication No. 2008-270584

However, since Patent Document 1 is not a method that does not use cerium oxide at all, it is difficult to say that the polishing material of Patent Document 1 is completely oxidized Cerium replaces abrasive materials. In addition, by mixing zirconia, the zeta potential of the surfaces of the cerium oxide abrasive grains and the zirconia abrasive grains will change, and there is a concern that the dispersibility of the abrasive and the residue on the substrate surface after polishing will increase.

Furthermore, in Patent Document 2, since SiO ₂ derived from the glass substrate is bound to the colloidal silica particles, the shape of the colloidal silica tends to be spherical, resulting in a decrease in the polishing rate. In addition, since the colloidal silicon dioxide has a special shape, even if the surface scratches of the substrate are suppressed, minute defects that may become fatal defects of the reticle substrate are easily generated.

In view of the above circumstances, the object of the present invention is to provide a The colloidal silica polishing material that exhibits excellent polishing rate in the polishing step of the synthetic quartz glass substrate, and can suppress scratches and minute defects on the surface of the substrate, and a method for manufacturing the synthetic quartz glass substrate using the same.

In order to solve the above-mentioned problems, the present inventors focused on colloidal silica abrasive grains used for polishing synthetic quartz glass substrates and actively conducted reviews. As a result, it was found that by mixing spherical and converging colloidal silica abrasive particles with mutually different average primary particle diameters and degrees of convergence, the average primary particle size of condensed colloidal silica abrasive particles is greater than true The average primary particle size of the spherical colloidal silica abrasive grains is polished. During grinding, the spherical spherical colloidal silica abrasive grains removed from the substrate by centrifugal force are less than the condensed colloidal silica abrasive grains. Suppress minor defects on the substrate surface and obtain high smoothness. And, by using the polishing material of the present invention, the polishing can be improved for all large or all kinds of substrates Speed, thus completing the present invention.

Here, in the present invention, the true spherical colloidal silica means that the shape of the silica particles is true spherical with an average true sphericity of 1.0 to 1.1, preferably an average primary particle diameter (D1A) of 20 to 120 nm , Colloidal silica dispersed in colloidal form with a meeting degree (n1) of 1.5 or less. Here, the average sphericity refers to the average value of the ratio of the largest diameter to the smallest diameter of each particle when 100 silicon dioxide particles are randomly taken. In addition, the so-called condensed colloidal silica refers to agglomerates of true spherical colloidal silica particles, preferably having an average primary particle diameter (D1B) of 70 to 200 nm and a convergence degree (n2) of 2.0 or more. Colloidal silicon dioxide.

Accordingly, the present invention provides the following methods for manufacturing colloidal silica abrasives and synthetic quartz glass substrates.

[1] A colloidal silica abrasive material, which is characterized by containing a colloidal solution containing true spherical colloidal silica abrasive particles and convergent colloidal silica abrasive particles.

[2] The colloidal silica abrasive as described in [1], wherein the average primary particle size (D1B) of the aforementioned colloidal colloidal silica abrasive particles is greater than the average primary particle size of the true spherical colloidal silica abrasive particles (D1A).

[3] The colloidal silica abrasive as described in [1] or [2], wherein the average primary particle size (D1A) of the spherical spherical colloidal silica abrasive particles is 20 to 120 nm.

[4] The colloidal silica abrasive as described in any one of [1] to [3], wherein the average primary particle size (D1B) of the convergent colloidal silica abrasive particles is 70 to 200 nm.

[5] The colloidal silica abrasive material as described in any one of [1] to [4], wherein the meeting degree (n1) of the aforementioned spherical spherical colloidal silica abrasive particles is 1.0 to 1.5.

[6] The colloidal silica abrasive material as described in any one of [1] to [5], wherein the convergence degree (n2) of the convergent colloidal silica abrasive particles is 2.0 to 3.5.

[7] The colloidal silica abrasive material as described in any one of [1] to [6], wherein the content of the spherical spherical colloidal silica abrasive particles in the colloidal silica abrasive material is relative to the convergent type The ratio of colloidal silica abrasive particles is 2 to 5 times the amount (mass ratio).

[8] A method for manufacturing a synthetic quartz glass substrate, which uses the colloidal silica polishing material described in any one of [1] to [7] for semi-final polishing in the manufacturing step of a synthetic quartz glass substrate Step or final grinding step.

According to the present invention, it is possible to obtain a polishing rate faster than that using conventional colloidal silica, and to suppress minute defects on the substrate surface, and to obtain high smoothness. In addition, it can also be used as a substitute for cerium oxide when polishing from a rough surface, which can solve the recent rare earth problem.

Hereinafter, the present invention will be described in detail.

The abrasive particles of the colloidal silica used for polishing the substrate of the present invention are produced by hydrolyzing organic silicate compounds such as water glass or alkoxysilane, especially those with different average primary particle sizes and degrees of convergence Colloidal silica abrasive grains with different shapes of spherical and convergent.

Here, the reasons for using colloidal silica particles of different shapes are as follows.

Generally, when grinding substrates such as synthetic quartz glass, colloidal silica abrasive particles are used in the final grinding step. The reason for this is that by using colloidal silica having a small particle size and a smooth particle surface as compared with polishing particles such as cerium oxide, a substrate with low defects and a highly smooth surface can be produced. However, because of the small particle size, the polishing rate is slow. As a polishing step, the substrate surface can only be polished by a small amount, and it is difficult to say that it is a polishing particle with grinding power.

However, when using abrasive materials in which colloidal silica abrasive grains of different particle sizes are mixed, the space occupancy rate of the colloidal silica abrasive grains per unit volume becomes larger, and as a result, the probability of the abrasive grains colliding with the glass substrate is increased, which can improve grinding force.

That is, the space in the most densely packed structure per unit volume constructed from convergent colloidal silica abrasive grains having the same average primary particle diameter enters the average primary particle diameter smaller than the aforementioned colloidal silica abrasive grains Spherical colloidal silica abrasive particles can increase the filling rate per unit volume and obtain abrasive particles with grinding power.

In addition, by mixing colloidal silica particles of different shapes of spherical and confluent types, the three-dimensional characteristics of the individual are drawn. In addition to the further improvement of the polishing rate, the defects on the surface of the substrate are also achieved. The number is reduced and the smoothness is improved.

The mechanism is described in detail below.

Convergent colloidal silica particles are deformed compared to the spherical spherical colloidal silica abrasive particles, so the contact area of the abrasive particles with the substrate is small and close to point contact. Therefore, the force transmitted from the polishing platen to the substrate through the polishing particles can be increased, and the grinding force can be increased.

A unit consisting only of converging colloidal silica particles Although the filling structure in the cubic volume has voids where no particles exist, by mixing the spherical spherical colloidal silica abrasive grains to fill the voids, the grinding force is further improved, and as a result, the polishing rate can be improved.

Moreover, the average of the two colloidal silica abrasive particles The secondary particle size (D1) is preferably the average primary particle size (D1B) of the colloidal colloidal silica abrasive particles is larger than the average primary particle size (D1A) of the true spherical colloidal silica abrasive particles.

Although the colloidal silica abrasive particles can improve the grinding force, the surface shape of the abrasive particles is deformed, so that the surface roughness of the substrate surface may become coarse. On the other hand, if the surface of the substrate is polished with true spherical colloidal silica abrasive grains, a substrate surface with low defects and high smoothness can be obtained. At this time, if the colloidal silica particles involved in the grinding are considered to exist in the rotating system, the average primary particle size of the colloidal silica abrasive particles will be greater than the average primary particle size of the true spherical colloidal silica abrasive particles, Due to the preferential removal of the condensed colloidal silica abrasive particles from the substrate surface due to centrifugal force, it is possible to achieve the grinding mode from the above-mentioned condensed colloidal silica abrasive particles followed by true spherical colloidal silica abrasive particles Style, so better.

Here, the average of the spherical spherical silica abrasive particles The secondary particle diameter (D1A) is preferably 20 to 120 nm, more preferably 40 to 100 nm, and most preferably 50 to 100 nm. When the average primary particle size of the spherical spherical colloidal silica abrasive particles is less than 20 nm, the abrasive particles in the cleaning step after grinding may be difficult to remove, and minute convex defects may remain as residues. On the other hand, when the average primary particle size of the spherical spherical colloidal silica abrasive particles is greater than 120 nm, it is difficult to be accommodated in the void formed by the condensed colloidal silica abrasive particles, so the grinding as an abrasive particle cannot be sufficiently improved The situation of the defect of power.

And, the meeting degree of the spherical colloidal silica abrasive particles (n1) is preferably 1.5 or less, and more preferably 1.0 to 1.5. When the meeting degree of the spherical colloidal silica abrasive particles is greater than 1.5, it cannot fully enter the voids formed in the filling structure formed by the colloidal colloidal silica abrasive particles, and the filling rate per cubic volume cannot be sufficiently increased. Therefore, it may not be possible to increase the grinding force, and it is difficult to obtain an effect that is consistent with the increase in the grinding rate. In addition, the degree of convergence is determined by the degree of convergence (n)=average secondary particle diameter/average primary particle diameter, the average primary particle diameter is converted from the measured value of the specific surface area obtained by the BET method, and the average secondary particle diameter is derived from red The scattering intensity of the dynamic light scattering obtained by the laser is measured and calculated.

On the other hand, the level of converging colloidal silica abrasive grains The average primary particle size (D1B) is preferably 70 to 200 nm, more preferably 70 to 170 nm, and most preferably 80 to 150 nm. When the average primary particle size of the condensed colloidal silica abrasive particles is less than 70 nm, the particles tend to be spherical and cannot be charged. It is difficult to increase the grinding rate due to the grinding force. On the other hand, when the average primary particle size of the condensed colloidal silica abrasive particles is greater than 200 nm, the specific gravity of the colloidal silica particles themselves will increase, and there may be defects in poor dispersibility.

In addition, the convergence degree (n2) of the colloidal colloidal silica abrasive particles is preferably 2.0 or more, and more preferably 2.0 to 3.5. When the convergence degree of the colloidal silica dioxide abrasive particles is less than 2.0, there may be a defect that the particles cannot be sufficiently deformed to induce the grinding force.

The spherical spherical colloidal silica abrasive particles in the colloidal silica grinding material should be mixed in a ratio of preferably 2 to 5 times (mass ratio), more preferably 2 to 4 times the amount of convergent colloidal silica abrasive particles. . When the content ratio of the spherical spherical colloidal silica abrasive grains is less than twice the amount of the colloidal colloidal silica abrasive grains, a defect that the surface roughness of the substrate deteriorates may occur. On the other hand, when the amount of true spherical colloidal silica abrasive particles is more than 5 times, the influence of the true spherical colloidal silica abrasive particles becomes the dominant role during grinding, so the grinding force is small, and it is difficult to effectively increase the grinding rate Situation.

In addition, the ratio of true spherical colloidal silica abrasive particles to convergent colloidal silica abrasive particles is preferably 50 to 80 parts by mass, more preferably 50 to 75 parts by mass of true spherical colloidal silica abrasive particles. , Even better for 60~75 parts by mass. On the other hand, the condensed colloidal silica abrasive particles preferably contain 20-50 parts by mass, more preferably 25-50 parts by mass, and even more preferably 25-40 parts by mass. The total amount of the spherical colloidal silica abrasive grains and the convergent colloidal silica abrasive grains is 100 parts by mass. The mixture of these abrasive grains in the abrasive is preferably 25-50% by mass, particularly preferably 35-50. quality %.

The colloidal silica abrasive particles used in the present invention can be borrowed more Examples of such production methods include methods such as granulation from water glass and hydrolysis of organic silicate compounds such as alkoxysilanes. The liquidity of the dispersion liquid containing these colloidal silica abrasive particles is preferably weakly alkaline from the viewpoint of the preservation stability of the colloidal silica, but it can also be used on the liquid side of the neutral or acid side. Colloidal silica is usually used dispersed in water, but alcohols such as ethanol and isopropanol, ketones such as acetone or methyl ethyl ketone, aromatic compounds such as benzene, toluene and xylene can also be used. Or these organic solvents or mixed solvents of water, etc. are used as the dispersion medium.

The colloidal silica abrasive material of the present invention can be used to The colloidal silica abrasive particles and the condensed colloidal silica abrasive particles are dispersed in a dispersion medium and prepared as a colloidal solution (colloidal silica dispersion). Moreover, the colloidal silica abrasive of the present invention can also be produced by combining commercially available colloidal silica dispersions. For example, as a dispersion of true spherical colloidal silica, there are SNOWTEX series manufactured by Nissan Chemical Industry Co., Ltd., COMPOL-50, COMPOL-80, COMPOL-120, and COMPOL-EX III manufactured by FUJIMI INCORPORATED. , DuPont-made SYTON, Mazin, etc., as the dispersion of colloidal colloidal silica, examples include Nissan Chemical Industry Co., Ltd. ST-UP, ST-OUP, Tama Chemical Industry Co., Ltd. TCSOL series, Fuso PL series of chemical industry (stock) system etc.

Using the polishing material of the present invention to polish a synthetic quartz glass substrate When the substrate is waiting, you can select the appropriate grinding accelerator and put it in an appropriate amount according to your needs. Into. By adding a grinding accelerator to the grinding material, the electric double layer around the colloidal silica abrasive particles can be stabilized, so it is expected that the dispersibility can be improved and the grinding rate can be sustained and fast. Examples of the grinding accelerator include polyacrylic acid, polyacrylate, poly(meth)acrylic acid, poly(meth)acrylate, formaldehyde condensate, and condensed phosphate. When blending a grinding accelerator, the blending amount is preferably 10 to 20% by mass for colloidal silica (solid content of the colloidal solution).

(直徑152.4mm)、8吋

(直徑203.2mm)之大小者，於大型基板時，可較好地使用G8(1,220×1,400mm方形)、G10(1,620×1,780mm方形)之大小者。 Examples of substrates to be polished using the polishing material of the present invention include synthetic quartz glass substrates, lithium tantalate substrates, silicon substrates, glass substrates for HDD, soda-lime glass substrates, etc. However, the polishing of the present invention In particular, the material can be used in the polishing step when manufacturing synthetic quartz glass substrates used for polishing photomasks, nanoimprints, and liquid crystal filters. For example, when the size of the substrate is a rectangular substrate, the size of 5 inches square (127.0×127.0mm) and 6 inches square (152.4×152.4mm) can be used better. Use 6 inches

(Diameter 152.4mm), 8 inches

(Diameter 203.2mm), for large substrates, G8 (1,220×1,400mm square) and G10 (1,620×1,780mm square) are preferred.

The colloidal silica polishing material of the present invention can be preferably used in a semi-final polishing step or final polishing step performed after rough-grinding a substrate, for example, a musk leather polishing cloth or the like. When used in the final polishing step, the polishing pressure can be 60 to 200 gf/cm ² .

Moreover, the rough grinding is done by forming and annealing the ingot (annealing), slicing, chamfering, rubbing, used to make the substrate surface The mirror polishing step is carried out.

When the surface of the substrate is smoother and less defective, In the final step, the colloidal silica abrasive material of the present invention is used. In the final polishing step, colloidal silica abrasive particles with a smaller particle size can be used for grinding.

In addition, the polishing method using the polishing material of the present invention is generally It is a batch-type two-sided grinding, and it can also be implemented by single-piece grinding, piece-by-piece grinding, and combinations thereof.

[Example]

Examples and comparative examples are shown below to specifically explain the present invention, but the present invention is not limited to the following examples.

[Example 1]

The 6-inch square synthetic quartz glass substrate (6.35 mm thick) was rubbed and rough ground, and then put into final polishing. Use soft musk leather abrasive cloth, use true spherical colloidal silica abrasive particles (manufactured by Nissan Chemical Industry Co., Ltd., trade name SNOWTEX XL) with an average primary particle size of 50 nm and a convergence degree of 1.2 as the average primary particle size Colloidal dioxide with a SiO ₂ concentration of 40% by mass of 3 times the amount (mass ratio) of 100 times of the colloidal colloidal silica abrasive grains (made by Tama Chemical Industry Co., Ltd., trade name: TCSOL 704) of 100 nm and a convergence degree of 2.5 The silicon water dispersion is used as an abrasive. Using a two-sided grinding machine, the grinding pressure was 100 gf/cm ² and the grinding rate was 0.2 μm/minute.

After grinding, wash, dry and use laser confocal After the defect inspection of the optical system high-sensitivity defect device (made by LASER TECH Co., Ltd.), the number of defects above 50nm level was 1.5. And, after measuring the surface roughness (Ra) using an atomic force microscope (AFM), Ra=0.14 nm. Moreover, no scratches caused by abrasions or lapping were detected.

[Comparative Example 1]

Using the same material as in Example 1, using soft musk leather abrasive cloth, using spherical spherical colloidal silica abrasive grains (manufactured by FUJIMI INCORPORATED, containing an average primary particle diameter of 80 nm and a degree of convergence of 1.1, trade name: COMPOL -80) Colloidal silica aqueous dispersion with a SiO ₂ concentration of 40% by mass is used as an abrasive. Using a double-sided grinder, the grinding pressure was 100 gf/cm ² and the grinding rate was 0.07 μm/min.

After polishing, it was washed and dried, and after performing defect inspection in the same manner as in Example 1, the number of defects above 50 nm was 1.8. In addition, after measuring the surface roughness (Ra) in the same manner as in Example 1, Ra=0.14 nm. Moreover, no scratches caused by abrasions or lapping were detected.

[Comparative Example 2]

Using the same material as in Example 1, using soft musk leather abrasive cloth, using condensed colloidal silica abrasive particles (manufactured by Nissan Chemical Industry Co., Ltd., containing an average primary particle diameter of 110 nm and a convergence degree of 1.2) Name: SNOWTEX ZL) SiO ₂ concentration 20% by mass of colloidal silica aqueous dispersion as an abrasive. Using a double-sided grinder, the grinding pressure was 100 gf/cm ² and the grinding rate was 0.06 μm/min.

After polishing, it was washed and dried, and after performing defect inspection in the same manner as in Example 1, the number of defects with a level of 50 nm or higher was 2.1. In addition, after measuring the surface roughness (Ra) in the same manner as in Example 1, Ra=0.25 nm. Moreover, no scratches caused by abrasions or lapping were detected.

[Example 2]

之合成石英玻璃基板(厚0.775mm)進行摩擦、粗研磨後，使用與實施例1相同之研磨布，使用平均一次粒徑為60nm、會合度為1.3之真球型膠體二氧化矽研磨粒(FUJIMI INCORPORATED製，商品名：COMPOL-120)為平均一次粒徑為90nm、會合度為2.8之會合型膠體二氧化矽研磨粒(扶桑化學工業(股)製，商品名：PL-7H)之4倍量(質量比)之SiO₂濃度35質量%之膠體二氧化矽水分散液作為研磨材。使用兩面研磨機，研磨壓為100gf/cm²、研磨速率0.07μm/分鐘。 8-inch sliced

After the synthetic quartz glass substrate (thickness 0.775mm) was rubbed and rough polished, the same polishing cloth as in Example 1 was used, and true spherical colloidal silica abrasive particles with an average primary particle size of 60nm and a convergence degree of 1.3 were used ( FUJIMI INCORPORATED, trade name: COMPOL-120) is the 4th type of colloidal colloidal silica abrasive particles with an average primary particle size of 90 nm and a convergence degree of 2.8 (made by Fusang Chemical Industry Co., Ltd., trade name: PL-7H) No. 4 A double amount (mass ratio) of colloidal silicon dioxide aqueous dispersion with a SiO ₂ concentration of 35% by mass is used as an abrasive. Using a double-sided grinder, the grinding pressure was 100 gf/cm ² and the grinding rate was 0.07 μm/min.

After polishing, it was washed and dried, and after performing defect inspection in the same manner as in Example 1, there were 2.0 defects of 50 nm level or higher. In addition, after measuring the surface roughness (Ra) in the same manner as in Example 1, Ra=0.17 nm. Moreover, no scratches caused by abrasions or lapping were detected.

[Comparative Example 3]

The same material as in Example 2 was used, a soft musk leather abrasive cloth was used, and a spherical spherical colloidal silica abrasive grain (manufactured by FUJIMI INCORPORATED, containing a mean primary particle diameter of 80 nm and a degree of convergence of 1.1, trade name: COMPOL -80) Colloidal silica aqueous dispersion with a SiO ₂ concentration of 40% by mass is used as an abrasive. Using a double-sided grinding machine, the grinding pressure was 100 gf/cm ² and the grinding rate was 0.01 μm/min.

After polishing, it was washed and dried, and after defect inspection was performed in the same manner as in Example 1, the number of defects above 50 nm was 2.8. In addition, after measuring the surface roughness (Ra) in the same manner as in Example 1, Ra=0.15 nm. Moreover, no scratches caused by abrasions or lapping were detected.

Claims (3)

A colloidal silica abrasive, which is characterized by containing spherical spherical colloidal silica abrasive grains with an average primary particle diameter (D1A) of 20 to 120 nm and a convergence degree (n1) of 1.0 to 1.5 and an average primary particle diameter ( D1B) is a colloidal solution of condensed colloidal silica abrasive grains of 70 to 200 nm and a degree of convergence (n2) of 2.0 to 3.5, wherein the average primary particle size (D1B) of the aforementioned colloidal colloidal silica abrasive grains is greater than that of a true sphere The average primary particle size (D1A) of colloidal silica abrasive particles. The colloidal silica abrasive material according to claim 1, wherein the content of the spherical colloidal silica abrasive particles in the colloidal silica abrasive material is 2 to 5 times the amount of the colloidal colloidal silica abrasive particles ( Mass ratio). A method for manufacturing a synthetic quartz glass substrate. In the manufacturing step of a synthetic quartz glass substrate, the colloidal silica polishing material according to claim 1 or 2 is used in a semi-final polishing step or a final polishing step.